diff --git a/backend/src/langs.ts b/backend/src/langs.ts
index ff52c65..ee75ce5 100644
--- a/backend/src/langs.ts
+++ b/backend/src/langs.ts
@@ -1482,6 +1482,14 @@ binding_irb.run(IRB.conf)
     template: `body:before {
   content: "Hello, world!";
 }
+`,
+  },
+  sed: {
+    aliases: ["gsed"],
+    name: "Sed",
+    main: "main.sed",
+    run: "echo 'Reading from stdin...' >&2; sed -f main.sed",
+    template: `s/.*/Hello, world!/
 `,
   },
   sh: {
diff --git a/scripts/docker-install-phase3d.bash b/scripts/docker-install-phase3d.bash
index 1f4a4d2..6aa1983 100755
--- a/scripts/docker-install-phase3d.bash
+++ b/scripts/docker-install-phase3d.bash
@@ -12,6 +12,9 @@ scala
 # Scheme
 mit-scheme
 
+# Sed
+sed
+
 # Sh
 posh